Call transmitter



Jan. 5, 1943. R. F. MALLINA f y 2,307,525

CALL TRANSMITTER Filed Aprjil l', 1941 3 SheetsfSheet 2 Armee/FK.

k/o frs .4P l la I' 22@ l L| la Il Il 2a@ 26a,I l l T /M/E/VTOR l?. MALL/NA Jan. 5,l 1943.

R. F. MAL-UNA 2,307,525

CALL TRANSMITTER Filed April 1. 1941 Patented Jan. 5, 1943 CALL TRANSMITTER Rudolph F. Mallina, Hastings on Hudson, N. Y.,

assignor to Bell Telephone Laboratories, Incorporated, New York,'N

York

. Y., a corporation of New Application April 1, 1941, Serial No. 386,284

8 Claims.

This invention relates to call transmitters ofv the type in which the operation of digit-numbered key members operate vibrative elements in the field of a magnet for generating alternatingcurrent impulses in a telephone line circuit corresponding to the digits of the operated key members.

The object of the invention is the provision of a call transmitter of the type above mentioned which will be simple in construction, cheap to manufacture, and positive in operation.

In accordance with the invention, a number oi bars which are movable longitudinally in upright members forming parts of a frame supporting the transmitter-operating mechanisms are actuated in a plurality of predetermined combinations by pairs of camming elements carried by manually-operable keys, which are mov-j able longitudinally in the supportingrframe` 'at' right angles to the bars. Meanscarried by the bars is provided for moving operatively-associated vibrative elements into pretensioned positions upon the movement of the bars in one of two directions, with other means carried by the bars for actuating operable members in the abovementioned combinations for releasing the vibra-- tive elements upon the movement of the bars in the other direction as efiected by the operation of the keys, each of the keys being provided with a retractile spring in the form of a metallic tape of arcuated cross-section, such spring oiering maximum resistance t a force tending to change itscurved surface, while offering a minimum resistance to such force when its arcuated shape has been flattened, the change in shape of the retractile spring occurring at the point where the depressed key and the bars actuated thereby reach a predetermined point toward their operated positions.

Other novel features and advantages of the invention will be apparent from the following description and by the claims appended thereto, reference being had to the accompanying drawings in which:

Fig. i is a top View of the casing whichvhouses the call transmitter mechanism of the invention, the keys being shown in normal non-operated position;'

Fig. 2 is a side elevation of Fig. l, partly in section, showing the left-hand side of the transmitter mechanism;

Fig. 3 is a top view of the transmitter mechanism showing the operating parts in normal position;

Fig. 4 is a front elevation shown with a number of operating parts partly'in section;

Fig. 5 is a right side elevation showing a number of operating parts with portions broken away;

Fig. 6 is a horizontal sectional View taken` on line -G of Fig. 4;

Fig. 7 is a front elevation showing a number of operating parts in section with one of the keys and a number of parts actuated'thereby partly operated;

Fig. 8 is a View similar to that of Fig. '7, but showing the key and parts controlled thereby in their fully operated position; v

Fig. 9 is a horizontal View taken on line B-VS of Fig. 4;

Fig. 10 is a view in perspective of one oi the key members shown in operative relation with two elements vof the reed-controlling mecha-I nism; and

Fig. 11 is a set of curves showing the tension characteristics of the retractile springs used in the call transmitter of the invention in relation to a well-known coiled tension spring,

Referring to the drawings, a set of key members KI, K2, K3, K4, K5, KS, Kl, K8, K9, and KH! are mounted for longitudinal movementon a frame consisting of a base II, two upright supports I2 and I3 secured to the base by a plurality of screws W and Wl, a spacer plate I4 secured at its end to the upright supports I2 and i3 by screws I5 and I6, and a plate or cover I1 secured by a number of screws i8 to lug portions carried by the supports l2 and I3 at the top end thereof, the key members KI, K2, K3, etc., being guidedV in their longitudinal movement at their lower ends in rectangular openings in spacer member Iii and at their upper ends in circular holes in the cover plate Il.

The keys KI, K2, K3, etc., are each provided at their lower ends with a retractile spring i9 normally holding these keys in the non-operated position as shown in Figs-1, 2, l and 5 Where the collar portions 25) of these keys abut against the underside of cover plate l1.

The upright supports I2 and E3 are each` provided with ve rectangularly-shaped openings OP and OPI provided for slidably receiving U- shaped bars ZI, 22, 23, 2li and 25 best seen in Figs. 2, 5, 6 and 9, these bars being held in their normal non-operated positions by retractile springs 2Ia, 220 23a, 24a. and 25a, respectively, each in the form of a piece oi metallic tape curved latitudinally and provided with slots ST, shown in Fig. 5, at their upper ends engaged by screws 25 threading inlugs 2lb, B2b, 23h, 24h

and 25h formed with an angle piece AP secured to the top outer disposed portion of upright I3, by screws SCS, while their lower disposed ends are secured by screws 26a. to lugs 2|c, 22e, 23e, 24o and 25o formed with an angle piece API secured by screws SCSI to the upright support I3, the bars 2|, 22, 23, 24 and 25 being provided with projections 2|d, 22d, 23d, 24d and 25d for engaging their retractile springs 2|a, 22a, etc., as for practical reasons at different points along their lengths as shown in Figs. 4, 7 and 8.

The bars 2|, 22, 23, 24 and 25 are moved from the position shown in Figs. 3, 4 and 6 to the positions indicated by bars 24 and 25 shown in Figs. 8 and 9 by the operation of key members KI, K2, K3, etc., each carrying a pair of cam elements such as CI and C, engaging bearing portions BP and BPI formed by slots SL cut into the bar for operation in the following combinations:

Key KI operates bars 22 and 24. Key K2 operates bars 2| and 25. Key K3 operates bars 22 and 25. Key K4 operates bars 2| and 24. Key K5 operates bars 2| and 22. Key K6 operates bars 25 and 24. Key K1 operates bars 23 and Z4. Key K8 operates bars 23 and 25. Key K9 operates bars 22 and 23. Key Kl operates bars 2| and 23.

The bars 2|, 22, 3, 24 and 25 are each formed with a projection 3| and hook-shaped portion 33 formed for actuating respectively associated rightangle shaped pawl members 2|f, 221, 23f, 24j and 251 best seen in Figs. 3, 4, 6, '7 and 8 in a manner which will be hereinafter described in detail. These pawls are pivoted on a common shaft 32 journaled at both ends on lugs 33 and 34 formed with the upright support I2.

To the outer side of upright support |2 is securely mounted on a voltage generator in the form of metallic blocks Pl and P2 clamping a plurality of vibrative reeds 2|r, 221', 231, 241' and 251` therebetween by the tightening effect of screw 35, the free ends of reeds 2|, 22T, etc., extending through a coil 36 for operation between the poles of a permanent magnet 35a held in adjusted position on the end of blocks PI, P2 by a plate 36h interposed between the screws 35 and the block PI.

The free ends of reeds 2ST, 221, etc., are disposed in engageable relation with the horizontally disposed arm of pawls 2|f, 22f, 23j, 24f and 25f and with the projections 3| of bars 2|, 22, 2-3, 24 and 25, the latter serving for moving the vibrative reeds from their normal positions shown in full line in Figs. 8 and 9 to their flexed positions shown in Figs. 3, 4 and 6 by their retractile springs 2 a, 22a, 23a, 24a and 25a, bearing against the lugs 2|d, 22d., 23d, 24d and 25d of the bars.

The operation of the key members KI, K2, K3, etc., is effective to impart a longitudinal movement to the bars 2|, 22, 23, etc., through their camming portions C and lCI to cause the pivotal movement of pawls 2|f, 221, in the combination above mentioned for releasing their corresponding reeds and thereby causing their vibration between the poles of permanent magnets 35a, the windings of coil 36 being connected to the subscribers telephone line by the terminals TI and T2 shown n Figs. 4, 7 and 8.

The call transmitter thus constructed may be mounted into the stand STD of a telephone desk set having a base 49 to which a support I I is secured by a number of screws 42 shown in flection Fig. 2 with the plate tted into a recess 43, formed in the stand STD.

According to the operation of the call transmitter of the invention, supposing that it is desired to establish a talking connection with a subscriber having, for example, the telephone call designation MHW-7281 and considering the keys KI, K2, K3, etc., and therefore the bars 2|, 22, 23, etc., in normal position as shown in Fig. 4. The operation of key K6 representing the first digit of the call designation MHW-7281 above mentioned causes each camming portion C and CI of that key to move the bars 24 and 25 simultaneously to the points where the projections 3| of these bars as shown in Fig. 7 are moved clear of the reeds 241' and 251' with these reeds remaining in their flexed positions due to their abutment against the horizont-al arms of pawls 24 f and 251. 'I'he continued movement of key K6 and that of bars 24 and 25 is effective through their respective hook portions 30 to impart a small angular movement to the pawls 24f and 25j from the position shown in Fig. 7 to the position shown in Fig. 8 so as to release reeds 241' and 251' to cause their vibration between the poles of permanent magnet 36a for generating alternating current in the telephone line corresponding to the frequencies of reeds 241' and 251. The return movement of key K6 under the tension of its retractile spring |9 permits the return of bars 24 and 25 to normal position under the tension of their respective retractile springs 24a and 25a, thus moving the reeds 241' and 251- in their normal pretensioned position while rotating the pawls from the position shown in Fig. 8 to the position shown in Fig. 4 through the engagement of the springs 44 carried by these pawls in abutment against their respective bars 24 and 25 and the transmitter is now ready for the operation of key K4-H, the second digit of the call designation MHW-7281 above mentioned and the consequent vibration of the reeds 2| r and 241 caused by the operation of the bars 2| and 24 actuated by that key in the manner above described in connection with the operation of key K6 and the operation is continued for each of the digit keys forming the telephone call designation MHW- 7281;

The curve shown in Fig. 11 indicates the dein inches of the retractile springs 2|a-25a, 22a-24a and 23a V. S., the force. in grams applied at the middle length portions on springs 2| a and 25a by the projections 2|d and 25d of bars 2| and 25, at points substantially one quarter of an inch above the middle length portion applied on springs 22a and 24a by the projection 22h and 24d of bars 22 and 24 and half-inch from the middle length portion applied on spring 23a. by the projection 23d of bar 23 in relation to an ordinary tension spring LS.

The use of retractile springs having the characteristics shown in Fig. 11 due to the so-called collapse of these springs at the point corresponding to the engagement of the hook portion 3|! of bars 2|, 22, 23, 24 and 25'With the pawls 2|f,

2212231, 24f and 25j has been found to cause the operator to depress the keys to their full operated positions and thereby assuring proper transmitting of the signals.

What is claimed is:

1. In a call transmitter, a set of key members, a plurality of slidably movable elements actuated by said key members in predetermined combinations, a set of vibrative reeds, and a plurality of means actuated in said combination by means formed with said elements to cause the operation of said reeds upon the operation of said key members for transmitting a call.

2. In a call transmitter, a set of longitudinally movable key members, each of said key members having cam portions, a plurality of longitudinally movable bars actuated by movement of said cam portions in predetermined combinations, a plurality of pretensioned vibrative elements, and means actuated by the direct operation of said oars for releasing said elements in said combinations.

3. In a call transmitter, a set of key members, a plurality of longitudinally movable elements, means carried by said key members for operating said elements in predetermined combinations, spring means for yieldably holding said `elements in operative relation with the firstmentioned means, a set of vibrative reeds one for each of said elements held in pretensioned position under the tension of said spring means, means for holding said reeds in pretensioned position upon a partial operation of said longitudinally movable elements as effected by said key members, and means formed with said elements for operating the second-mentioned means for releasing said reeds in said combinations upon the continued operation of said elements by said key members.

4. In a call transmitter, a set of longitudinally movable key members, retractile springs for said key members, a plurality of longitudinally movable bars actuated by said keys, a retractile spring for each of said bars in the form of a piece of arcuate tape operable by the movement of said bars for decreasing their tension following a predetermined movement of said bars for controlling the operation of said keys, a frame for mounting said keys and said bars at right angles to each other, means carried by said frame for securing one end of each of said tape springs, other means carried by said frame for loosely supporting the opposite ends of said tape springs for permitting free bending thereof, a pair of cams carried by each of said key members for operating said bars in predetermined combinations, a set of normally tensioned vibrative reeds, and a mechanism actuated by said bars to cause the release operation of said reeds in said combinations for transmitting a call.

5. In a call transmitter, a frame comprising two upright supports, a pair of plates for holding said supports in parallel spaced relation to each other, a set of key members mounted for longitudinal movement in said plates, each of said ports and engaged by said cams for operation by the movement of said key members in predetermined combinations, spring means tensioned by the operation of said bars for returning the latter to normal following the return of said key members to normal, a set of vibrative reeds disposed in engageable relation with means formed with said bars and normally pretensioned by the tension of said springs, and a mechanism actuated by said bars for releasing said reeds in said combinations for transmitting a signal according to the operation of said key members.

6. In a call transmitter, a set of manually operable key members, a set of movable means actuated by said key members, a plurality of vibrative elements, a mechanism actuated by the operation of said movable means for causing the operation of said elements, and a plurality of springs tensioned by the movement of said movable means by said key members, said springs flexing variably upon the movement of said movable means for controlling the manual operation of said key members.

7. In a call transmitter, a set of key members, a set of operable elements actuated by said key members, a mounting for said key members and said operable elements, retractile springs for said elements secured to means carried by said frame, said springs being in the form of metallic laterally curved tapes, said springs aording maximum resistance to a force applied to said key members tending to change their curved surfaces and offering minimum resistance to such a force following a change of said curved surfaces for controlling the operation of said key members.

8. In a call transmitter, a set of key members, a set of movable elements actuated by said key members, a retractile spring for each of said ele` ments tensioned by the movement of the latter, each of said springs being in the form of a tape curved laterally, secured at one of its ends to a xed support, each of said springs oiering maximum resistance to a force tending to change its curved surface as at the beginning of the movement of one of said key members and oiering a minimum resistance at the point where said key reaches a given point along toward its operated position, said spring returning said operated key to normal unoperated position with a force which increases as the key nears its normal non-operated position.

RUDOLPH F. MALLINA. 

